Pu₃Ga or Pu_1-xGa_x, x = 0.25? Finding the “correct” solution using modeling methods that produce an infinite number of solutions for a material with potentially infinite configurations.

Of the phases of interest concerning the very storied “A Tale of Two Diagrams” within the Pu-science community, an intriguing narrative regarding American vs. Russian differences in the Pu-Ga phase diagram discovered after the Cold War, Pu₃Ga by far remains the most mysterious. Recent X-ray PDF data acquisition and subsequent small-/large-box models to said PDF for this phase appear to be revealing that this material is not an intermetallic compound with a well-defined stoichiometry. Rather, it is an alloy very similar to δ-Pu, albeit more gallium rich. This ultimately makes the solution space much wider, given that reverse Monte Carlo (RMC) methods can produce an infinite number of nearly degenerate solutions and alloys can have nearly infinitely many configurations in bulk form. A modeling scheme employing RMC methods has been developed to answer the title question, and discern which countries constructed Pu-Ga diagram is more accurate.